In recent years, in a construction machine having an upper slewing body such as a hydraulic excavator or a crane, by detecting an obstacle located in surroundings and stopping an operation or issuing an alarm according to a detection result, interference between the upper slewing body and the obstacle is prevented in advance.
Patent Literature 1 discloses a technique in which, when it is detected that an obstacle detected by a millimeter wave radar is located in a collision preventing region provided around a work machine and operation in a direction to approach the obstacle is performed, operation of an upper slewing body is forcibly stopped.
However, in the technique of Patent Literature 1, when directivity of the millimeter wave radar provided on the upper slewing body is directed toward the ground in order to widen a detection range, a lower travelling body is detected as the obstacle, and operation stops and alarms unnecessarily occur frequently.